The version of the kernel-unsupported rpm provided with the RHEL 3
easy ISOs image is for kernel version 2.4.21-1.1931.2.399.ent, whereas
the kernel that is installed by default is 2.4.21-4.EL As such, the
unsupported modules complain about being compiled against the wrong
kernel version and refuse to load.
The version of both rpms on rhn is 2.4.21-4.0.1.EL.